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By | Chris Mellor 13th October 2008 12:12

HDS sends in SAS to shoot up modular storage range

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Hitachi Data Systems has refreshed its mid-range AMS modular storage line, adding a SAS backplane to boost internal bandwidth and turning the two controllers into an active:active pair.

As noted here, the AMS (Adaptable Modular Storage) line has three models: entry-level AMS 200, mid-range AMS 300 and high-end AMS 1000. All sport one or two active:passive controllers, mixed Fibre Channel (FC) and SATA drives, and FC, SCSI and NAS support across the range.

There are three storage tiers: 15K FC; 10K FC; and 7.2K SATA. There is also RAID 6 protection against two drive failures, logical cache partitioning so that cache can be set aside for specific applications, virtual storage ports so multiple hosts can share the 4Gbit/s FC ports, support for Windows multi-path IO (MPIO), and power-saving drive spin-down.

There are three models in the new AMS 2000 line: AMS 2100; AMS 2300; and AMS 2500. These effectively replace the original AMS product trio. They now have active:active controllers. HDS calls these 'dynamic load-balancing' controllers, and all three models have 99.999 per cent availability - the five 'nines' benchmark.

They also have a SAS backplane, instead of using FC arbitrated loops (FCAL) as before for linking the drives to the controllers. This runs at 3Gbit/s and has up to 32 point-to-point links with a combined bandwidth of 9,600MB/sec. HDS says this is 'dramatically' faster than before.

The FCAL scheme had four 2Gbit/s connections per tray, adding up to a tray interface bandwidth of 8Gbit/s. There are now eight 3Gbit/s SAS connections per tray providing 24Gbit/s of tray bandwidth.

We suspect that HP's coming ExDS91000 also uses a SAS infrastructure to link its drive trays and processors. We might suppose that a 6Gbit/s SAS II scheme would provide a good fit for SAS interface solid state drive (SSD) use.

Supported host numbers have also risen. The AMS 200 and 500 handled up to 512 host connections with the AMS 1000 supporting 1024. Two of the new models manage more: the 2300 supports up to 1024 and the 2500 2048, while the 2100 stays at 512 connections.

HDS has rounded up an IDC analyst, Richard Villars, who says that the combination of SAS backplane and better controller pairing makes the new AMS products well suited to supporting virtualised servers. This is because they can be provisioned faster, have better performance, etc. etc.

What the new AMS boxes don't have is thin provisioning, which HDS calls dynamic provisioning and which it ships with its high-end USP-V arrays. This is coming in the first half of next year. With it you need only buy as much disk space as is needed for the data you are going to be writing in the near-term, while spoofing applications that they have fully populated volumes. For now you're going to have to buy all your AMS disk capacity up front.

HDS is also adding security and data protection additions to its USP VM arrays, the lower-end USP product.

AMS 2100 prices start from around $31,500, AMS 2300 from around $47,500, and AMS 2500 from about $81,500. The AMS 2100 and 2300 are available now, and the 2500 will be available in quantity from November.

HDS says there will be more information here. It will be interesting to see if HDS competitors - EMC, HP, IBM, NetApp and Sun for example - follow its lead in abandoning FCAL technology for internal drive to controller linkage. ®

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